Micro surgical examinations and operations require handheld instruments which enable objects or body tissue in a patient to be grasped, held and cut, where necessary. For actuating the handheld instruments lever-type handles or grip shells are provided which are hinged to each other about a joint pivot bolt and are manually pivoting against each other for actuating instrument branches coupled thereto. If the manual actuating force on the handles/grip shells is dropped, the latter have to be forced apart again so as to return the instrument branches into their home positions. This is achieved, for example, by appropriate tensioning devices within the instrument such as resiliently flexible leaf springs. Said leaf springs may be mounted, for example, as external elements between the handles on the same or may be arranged as a proximal extension of the instrument at the proximal ends of the handles preferably integrally with the latter. Irrespective of the respective arrangement of the tensioning device, usually they have in common that the free ends of the leaf springs arranged at each of the two handles are coupled to each other, thus forming a kind of in-line connection of two leaf springs.
In order to be able to move the surgical instrument inter alia into a cleaning position, in surgical handheld instruments of this species, in particular in micro-scissors, micro-tongs and micro needle-holders, the free spring ends are juxtaposed in a state released from each other so as to be able to open the surgical handheld instrument completely via the pivot or hinge pin. For a detachable coupling/connection of the free leaf spring ends, manual micro-instruments established on the market make use of so called through-connections. In several through-connections of this type a T-shaped tab provided at the free end of the one leaf spring is pushed through a rectangular opening at the free end of the other leaf spring by twisting the two spring ends. Although the spring ends are positively coupled via the T-shaped tab, a form closure having large play is formed, however, so that the spring ends are not correctly guided during the operating movement of the two handles. In so far the leaf springs as well as the handles are guided exclusively on the pivot pin which, accordingly, should be press-fitted into pivot bores at the shell-type handles without large play.
For example, from the state of the art microsurgical forceps are known as described in DE 29 19 271 C2. Hence DE 29 19 271 C2 discloses a manual forceps instrument consisting of two grip plates or grip shells connected to a proximal (not releasable) joint via flat spiral or leaf springs, said grip plates or shells including a forceps-type, scissors-type or other gripping or holding branch at their respective distal ends. The springs are mounted to be exchangeable on the grip shells or grip plates, respectively. The proximal joint in this case is formed by a hinge pin pressed with eyelets formed at the flat spiral springs.
The previously known solutions suffer from the following drawbacks, however:                Cleaning and conditioning of the surgical handheld instruments is difficult when the connection of the two leaf springs is not releasable, as the handles cannot be swiveled over any distance so as to reach as little overlapping of the handles and the instrument branches as possible in the area of the pivot bolt.        Through-connections according to the known principle of the T-shaped tab and a rectangular opening are comparatively easy to uncouple, but usually they have considerable play. Therefore, they are completely unsuited for guiding the free ends of the leaf springs and thus indirectly for guiding the handles.        A surgical glove may additionally be slightly clamped and thus damaged when handling a through-connection. This risk is given even in the case of surgical actuation of the instrument.        By strongly twisting the spring ends when inserting the T-shaped tab into the rectangular opening, the material may be stressed by torsion which may possibly cause plastic deformation of the leaf springs. This may entail the fact that the two handles are no longer swiveled exactly in parallel to each other and thus get jammed.        